Lead screw variator



1949 K. H. WILLS 2,492,251

LEAD SCREW VARIATOR Filed Jul-y so, 1945 e She'ets-Sheet 1 INVENTOR KURT H, WILLS.

ATTORN EYS Dec; 27, 1949 H; wins 7 2,492,251

LEAD SCREW VARIATOR Filed July 30, 1945 6 ShQ t s-S heet 4 luv u KURT H. WIL

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K. H. WILLS LEAD SCREW VARIATOR 6 She etsSheet 5 Filed July-30, 1

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Patented Dec. 27 1949 LEAD SCREW VARIATOR Kurt n. Wills, Sidney, Ohio, assignor to The Monarch Machine Tool 00.,

'- corporation of Ohio Sidney, Ohio, a

- Application July so, 1945, Serial No. 607,875

1: his, invention relates to machine tools, and .particularlmto thread turninglathes.

It is a particular ob'ectfof this invention to {s idemejansfin.a'thread'turning lathefor in- ,Viinit'ely varying-the effective pitch of the lathe [screw] 1 I ;ltis a otherflobject oi. this invention to prore i ir -cann ctien i a t rm lathe ror axially shifting the lead screw during is ips Q xa thread sa h tt pitch o the thr edmay,be v d a -sles r dos-o'e ctherso iect to r d si o @djiiSting-the eliectiye pitch of a lathe lead screw which desired correction V :is still another object to provide a mechanismaccording to the foregoing objects which maybe madeefifiective over any given portion of h t avel. o the-lath r ia e Th sez nd the e i an b come, more apparent on g reference to the vfollowing specification taken in connection with theaccg npanying drayvings in which: Figure 1 is a diagrammatic plan view of a lathe h;aving .a lead screw adjusting mechanism acco rding -tothis invention; Figure- 2 .is across section on line 22 of Fig- We and shows, the means ,for adjusting -the mechanism relative tothelathe carriage; Eignreii is; a crossrsection oncline 3+3 of Fig- ..ure- 1; that shows the; connecting means between :thel lathe carriage and the lead screw adjusting mechanism; ,r s v Figuregi is agsection on line 4-4 of Figure 2 and shows more indetail one of' the clamping collars associated, with the lathe carriage; Figure 5 is aplan'view partially broken away portion oi the lead screw adjusting mechaa verticallongitudinal jsectionvtaken ,of Figure 1 showin construcof. he lead screw adjusting mecha- -msm;,. r H 4 v fFigure'Z' is'a verticalsection taken on theline T ief- Figure and shows the gear train intera" ectingtlie adjusting mechanism with the 8 reuse v 1'9 and lflfare'detailed sections showing ari'ldjusting means "if T the giiid bearings in the mechanism; l. I I

i igiir l is a plja'n section showing the-ladjiistin'g means used in connection with Figure 1';

4 Claims. (C l, 825) my bejselectivelyadjustedrto give any advantages wil ovvs more indetailthe arrangement v 2 i i ,7

Figure 12 is a section'on the line l2-.-I 2 of Figure 7; and 7 Figures 13, 14' and 15 are'views of a modified form of drive into the lead screw adjusting mechanism. I Y Generalarrangement A lathe constructed according to this invention comprises, generally, a lathe bed having; a headstock and tailstock between which a.;wo rk piece is mounted to be driven by the headstock sp d -7' i 7' is A carriage is provided which-mounts a cu ing tool and which is reciprocate d longitudinally of the work piece by a lead screw; The lead screw is geared to the headstock spindle throughany appropriate arrangement including change gears so that a predetermined speed ratio maybe ,established between the said spindle and the said lead screw. 1

According to my invention means are provided for infinitely varying the speed ratios between the spindle and lead screw so that a thread having any predetermined pitch may be cut This mechanism comprises means for varying theeffective pitch of the lead screw as it drives the carriage longitudinally of the work piece.

In general, the adjusting means comprises a first member movable with the carriage and a second member movable transversely to the first member. An adjustable inclined plane interconnects the first and second member so that any amount of movement is given the second as the first moves relative thereto.

The movement of the second member is translated through a suitable gear train to a nut which engages a threaded sleeve carried by the lead screw. The lead screw is secured to the sleeve and is driven from the headstock through a solined connection so that as the said nut and sleeve are relatively rotated the leadscrew is given a predetermined amount of axial shift.

This "is effective continuously to vary the effective pitch of the lead screw as the'carriage moves along the work. i r I e Means comprising a graduated handwheel are provided for adjusting-the aforementioned inclined plane so that any predetermined adjustment may begiven the lead screw during the travel of the carriage. Other means are provided for causing the mechanism to be'eflective over any predetermined portion of the travel of-the saidcarriage. a vThe aforementioned first and second members include anti-friction bearings, preferably ball bearings, a portion of which are mounted on eccentric pins so that they may be adjusted very precisely to guide the said first and second movable members. Thus, precise adjustment of the lead screw is obtained so that screws and threads having odd or fractional pitches may be cut to the desired degree of accuracy.

The particular use contemplated for my invention is that of forming the threaded portions of dies and molds in which is desired to form work pieces which, when ejected from the mold and cooled, will have threads of standard pitch. By knowing the characteristics of the molding material, it is possible very precisely to add or subtract a predetermined percentage of pitch from the thread in the mold part corresponding with the percentage of shrinkage or expansion of the work piece. However, it will be apparent that my invention is also useful in many other instances where it is desired to cut grooves or threads having a pitch different from that provided for in the lathe gearing.

Structural arraagement Referring to the drawings, there is illustrated in Figure l a lathe comprising a bed I!) having the usual ways J2 thereon for guiding a carriage I4 longitudinally of the said bed.

The bed III a headstock l6 and a tailstocl i l 8 between which is supported a work piece :28 to'be driven by the lathe spindle 22 in any customary" manner. 'Ihe lathe also comprises a lead screw 24 which is connected by a splined connecter '26 and'a shaft 28 through a gear box and change gearing with the geared lathe headstock i8. By the usual change geararrangements within the gearbox a number of predetermined speed ratios between the spindle 22 and the leadsCrew 24 may be established. According to the usual practice, only a certain number of these ratios are available so that the turnfing of special threads generally requires the use of special change gears.

Fastened to the right end of the lathe bed You a platform 29'is a mechanism generally indicated at 38 which is for the purpose of axially shifting the lead screw 24 during the operation of the lathe. The mechanism at 38 com prises a stationary bed 32 which slidably receives a plate 34between the ball bearings A, B, C and D. The bearings A, B and C are supported on eccentric screws 36 which pass through the bed member 32 and are locked in place by nuts 38, Figure 10. The eccentric screws 36 provide a means whereby the plate 34 may be adjusted to move in exact parallelism with the carriage l4 while being exactly guided between the said ball bearings so that there is no side motion to the said plate. The fourth ball bearing at l) is generally 'fixedlycarried' on a pin'which is locked in the bed 32. V V

The plate 34 carries a second plate 48 which is pivoted -on thepin 14 2 at the leenter ofthe plate 34. The plate 48 is angularly adjustable about the pin '42 and may be locked inany posi tion of adjustment by bolts '44 which extend into the slots 46.

, V h plate 1 c m ris a 1 standing rib 48 which is adapted for being received between the ball bearings E, F, G and H.

The ball bearings F, G and H are carried by a substantially rectangular plate which is pivotally secured to a transverse bar 52. The transverse bar 52 is guided in a housing 54 which is secured to the bed portion 32 many suitable manner. The location of the housing 54 i s such 4 that it does not interfere with the free movement of the plates 34 and 40.

The member 52 extends leftwardly (Figure 8) and has secured to the left end thereof a rack 56 by the bolts 58. Disposed between the end of the member 52 and the rack 56 is a tapered gib 88 which is adjustable relative to the said member and rack by means of the screw 52. The plugs 84 provide a means of access to the bolts 58 so theymay be loosened to permit the adjustment of the gib 60. The purpose of the gib 68 is to take up for wear and prevent any lost motion between the rack 56 and the gear 66 which meshes with it. The gear 66 is rotatably mounted on a stud 68 and has integral therewith the gear it whieh meshes with a gear 72. The gear 12 is rotatable on a supporting shaft 14 and has integral therewith a gear 18 which meshes with a gear 18. The gear 18 (Figure 7) is integral with a structure which comprises tubular portions which extend oppositely away from said gear and one which is internally threaded as at e6. The tubular portions are supported in journalled apertures in the housing portions 82 and 84 which are secured together in any suitable manner. Longitudinal movement of the gear [8 and the tubular portion integral therewithis prevented by the wear plates 86 disposed between said gear and thehousing portions 82 and84.

Threadedly received within the nut 88 is a screw 88 which is hollow and which abuts ateither end the ball thrust bearings 90. The lefthand thrust bearing abuts a shoulder 92 on the lead screw 24 while the right hand bearing!!! is abutted by the nut and washerarrangeinent at 94 and carried by the threaded end of the lead screw. The screw 88 is further supported by the radial bearings 96 at either end so'that it is fixedly but rotatably held in position relative to the lead screw. Rotation of the screw 88 is prevented by the splined connection thereof at 98 with the sleeve 1-00. The sleeve [00 is' carried in an aperture in the right end of the housing 84 and is held against rotation by the screws I02.

It will be apparent that transverse movement of the member 52 will be effective through the rack 56 and the gear train associated therewith to rotate the nut 88 thereby axially to shift the screw 88 and with it the lead screw 24. I

Referring to Figures 5 and 8, the manner of guiding and supporting the plate 34 is more particularly shown. The plate 34 comprises ledges I04 on either side thereof which are adapted for being received under the projecting plates I86 on either side of the plate'34. The plates I06 are secured to the bed' 32 by the screws I88 and are apertured to receive the ends of the eccentric screws 36. The plate 34 is vertically supported on the wear plates lI-O positioned in suitable shaped recesses in the bed 32 beneath the said plate 34 Referring to Figures 6 and 8, the means for supporting the plate 50 in the member 52 is more particularly shown. The plate 50 c0mprisesan upstanding portion I12 which is closely received Within a shouldered bushing I [4, the shoulder of which lies between the member 52 and the plate 50. A nut I I6 secures the bushing I [4 in the prop,- er relationship relative to the member 52 while the nut H8 secures the member 5.0 and portion H 2 thereof in proper relationship to the said bushing. The plate 5!! .is thus accurately rotatably supported by the member 52. 7

Re e in iofiau e .6 an a a s a e l d u t n th Pl t A." lat fi to the the plate is in the plate 34 will beseen to comprisea rackI secured to the end of the plate 40 and adapted for meshing with a spur gear I22 which is rotatably -mounted onthe pin I24 and the block I26.

- meshes with the gear I22. The gear I28 has attached thereto the worm gear I30 which is engaged .by theworm I32. The worm I32 is-carried on-a shaft I34 which projects outwardly of the casing I26 and has secured thereto the graduated handwheel I36. The graduated handwheel I36 has the dial I38 thereon, while. the member I40 secured to the housing I 26 has an index mark I42 adapted for registration with the said dial.

The plate 40 also carries a dial plate I44 which is adapted for registration with the index mark I46 which is carried on the cover of the housing I26. By loosening the bolts 44, the handwheel I36may be actuated to drive the rack I20 angularly :to movethe said plate'40 in any predeter- --mined position of adjustment.

The precise amount of adjustment may' be indicated on the dials I44 and I38 and the bolts 44 tightened when desired position.

Operation I In operation, the work piece 20 is mounted {in the lathe with the carriage and cross slideinitiallypositioned at'the beginning of the cut. The

" gears in the lathe'headstock are adjusted so as to 'drive'the lead 'screw' 24-at the nearest speed to that required for cutting the necessary thread.

Thereafter, the plate 40 is adjusted so as axially to shift the lead screw during the movement of the carriage in order to add to or subtract from the movement of the carriage therebyexactly to cut the necessary thread. In order to permit the carriage I4 to' be initially positioned,- there'are provided the collars I50 on the 'rod I52 (Figures 2' and 4) which abut either side of a bracket I54 carried on the under side of the carriage I4 The collars I50 may be loosened so that relative ad- "justment of the'carriage and the rod I52ma'y'be.

made before putting the lathe in operation. The rod I52 is connected to a bracket I56 (Figure 6) which is secured to the end of plate 34 by "the 'bolts I58 so that when the collars I50 are locked against the bracket I I54, the carriage I4 and plate 34 move as an integral unit.

Wh'e'n' the feed rod 24 is driven in the conventional manner from the lathe gearbox it longitudinally drives the carriage I4 in the customary manner. Since the rod I52 is directly connected to the carriage I4 by the bracket I54 and collars I50 this rod I52 also reciprocates as a unit with the carriage I4. Reciprocation of the rod I52 by means of the bracket I56 reci-procates the'plate 34. With the pivoted plate 40 at an angle to the plate '34 the upstanding rib 48 transmits through the bearings E; F; G'and H a transverse movement to the member 52; "This transverse movement through the rack 46 and gear train 66--'I8 rotates the nut 80. Rotation of the" nut 80 through the screw 88 and thrust bearings 90 causes an axial shiftingof the 'lead screw '24. This slight axial shifting is permitted by the splined connection 26. Thus, it will be seen that with the slight axial shifting of the lead screw 24 the effective pitch of the thread of this lead screw 24 is changed. Such change may be very slighta fraction of one per cent if desired in order to account for shrinkage in a material which is to be molded in the threaded mold.

s *Modification of Figuresis, 14cm: 15 1' 'is a substitute for the plate 34 of the preferred e bodiment. This plate I60 carriesthe plate 40 having'the upstanding rib 48 which is adapted to b Iangularly positioned relative to the direction iof ti anslation of the plate I60 and thus provide a ransvers'e movement as in the preferred emir ne'nt. The plate I60 has connected thereith,;}by the screw I62 and dowel I64, a nut I66 which is engaged by a screw I68 journaled in block l 'l0." The thrust bearings I I2 retain the "screw I68 against axial movement relative to the bed I I4 and the gear II6 provides means for driving the said screw in rotation. The bed I14 is adapted to "be fastened to the right end ofthe "'lathe'in any suitable manner, and is the equivalent of the bed '32 of the preferred embodiment.

In Figure 14 it will be noted that the lathe lead screw II8 carries a gear I80 and that the bed I" carries-a stub shaft I82-that supports a gear I84. "The gear I84 is mounted on an anti-friction'bear- 'ing I86 that is slidable on the stub shaft I82 so that the gear I 84 may be selectively positioned to drivingly interconnect the gears I16 and I80 or to disconnect the said gears.

Pivotally mounted at I88 is a lever I90 which comprises slotted shoe I92 engaging the periphery of thegear- I84 for shifting the gear as mentioned The end of the lever opposite the shoe ha [a springlpressed plunger I94 adapted for engage- -ment with spaced holes in a plate I96 so that the 'lever I90 and, therefore, the gear I84 may be selectively locked in a first-position drivingly to interconnect the gears I16 and I80 or, in a second-position to disconnect the said gears. Thus, this modification of Figures 13, 14 land 15 provides fortranslation of the plate I60 (the equivalent of plate 34) by .a gear train from the lead screw -I'I8 rather than by direct coupling to the carriage I 4. The rod I52, collars I50, and brackets -tI 54 =and-I 56 thus are-eliminated in this modificaion. -While it is preferable that the pitch of the screw I68 and the size of the gear I16 be appor- -tioned to the pitch of the lathe lead screw I18 and the gear I80 keyed thereto so that the plate -I60-= an'd the lathe carriage move together, it is not-intended that this invention be limited to I that particular arrangement. 1

1 Inm'achine shop and tool room practice, it is often desired to form a thread whose pitch is a predetermined percent diiferent from a standard pitch.- T'his 'occasion would arise, for example, inthe forining of threaded parts formolds to be tised for plastic molding and similar operations. .In-this case, the present invention permits the threadto be formed on the mold part with a predetermined amount allowed for shrinkage or expansion so that work pieces made in the molds will,.-whe'n completed, h'avethreads therein of the proper pitch.

It will be evident that this invention is also useful for forming threads having a pitch different from that provided for in the headstock change gearing. Thus, a lathe may be constructed which has a substantially greater range than has heretofore been possible and the utility ianozgati of the inachine isthereftire:enhancd'without the necessity of providing a great quantity :of change 'el a. i V ill also be evid entthat while the workpiece is'h r lias exte rial'thread thereon, this device :is "eguan adapted 'for turning internal threads,

the only ldifierence being'in the location of the cutting tool relative'toth'e work.

I Also, while the drawings illustrate the preferid, embodiment Qof myinvention, it will be understood that'varioiis changes can be made thereinwithout departing from the spirit of this jqiselqsare. Fbr'eitample, although it is preferable tofcag'rry the ball bearings 'A, B, C and D in the be'g13'2, 'theycouldTaswellcarried by the plate '4 without involving any departure from this invention. :Other inversions of the device will be apparent to those-skilled in the art and it is inli iieb iflrbia itleii f sai e ,sdrew, abutment means for. preventing relative axial movement of "said leadscr'ew andsaidiirst member, a second threaded memberfor engaging said first threaded.

n ieimber 'wherebyrelative rotation of said mem- 1ber iiseperehle ia y. Q sh id lead Screw, a first plate adapted for movement parallel to said carriage, n eans interconnecting said carriage and saidplate for causing simultaneous movement ,thereoi, a secqnd 'plate pivotally secured to said firstplate comprisingjan upstanding rib, means for adjusting said plates to any predetermined angiilarity, a bar movable in a path which intersects the path of saidplates, means carried by said bar:for engaging said rib on either side thereof, a rack carried by said bar, and gearing interconnecting said rack and one of said threaded members whereby movement 'of said carriage is adapted for-axially shifting said-leadscrew at a predetermined rate thereby to 'modify the movement of said carriage,

2, Ina'machine 1500].,3, carriage, a'lead screw, splined means for driving; said lead screw for ac- "tuating said carriage, a first threaded member mounted on-said lead screw so as to permit relative rotation while preventing relative axial movement of said mmberand said lead screw, a second threaded member for engaging said first threaded -member whereby relative rotation of said members is operable axially to shift said lead screwpa first-plate,-guide means for guiding said platein apathparallel. to said carriage, an adjlistable draw bar interconnecting said carriage and said plate, a secondplate carried by said first plate adjustable to anypredetermined angularity and comprising an'upstanding rib, a'bar constrained to move in a path which is transverse :tothe path of said plate, means pivotally secured to said bar comprisinganti-friction bearings for engaging 'sal'd rib on: either side thereof, and 'gearing interconriectirig saldba'r with one of-said threaded members whereby movement of said carriage is operable aiiially to "shift said lead screw threbytoinodify the'rate of movement of 'said' carriage.

3. In a machineftool, a carriage'a lead screw, splineddriving meansfo'r said lead Screw, a'hollow screw mou'nted'on'said lead screw, abutment meansfor preventing relativeaxial movement'of said hollow sc'rewand 'saidlead screw, stationary meansspliried to 'said 'hollowscre'w forprevent- 'ing rotation thereof, 'a nut thr'ead'edly engaged with said "-hollcw screw, a plate connected with said carriage for movement therewith, guiding means engaging either edge of said plate for guiding the same in'a path parallel with that of said carriage, amember'comprising an upstanding 'rib pivotally *moun'tedon-said. plate 'and adjustable 'to any pred'etermined angularity th'erewith, a bar-movable substantially at right angles to said plate, "a block pivoted to said bar and comprising anti-friction bearings adapted for engagingsaidrib on-either side thereof,'a-rack-connected .with'said bar,-'and agear train interconnecting said rack with-saidnut whereby'mov'ement of said carriage is efiective axially to shift said lead screw thereby'tdvary the effective pitch thereof.

4. 'In' a machine tool, a carriage, "a dead screw, splined' driving means for said leadscrew, a hollow screw mounted on said leads'crewjabutment means i or preventing relative "axial movement of said hollow screw and said lead screw, stationary meanssplined to said hollow-screw for preventing rotation thereof, -'a nut 'threadedly engaged with 'said hollow screw, a plate connected with sai'd'carriageior movement therewith, a stationary frame -for reciprocably receiving said plate, a plurality of antifri'ction bearings carried by said frame adapted for'engaging eitherdgeof said plate, said bearingsbeing-movable to adjust the pathof'said plate "i'nt'o precise parallelism with thepa'th'bf saidcarriagea member comprising an upstanding rib pivotallymounted on said plate and adjustable to any predetermined angularitytherewith, 'a bar -m'ovable substantially at right angles -to-said plate, ablock pivoted to said bar and comprising anti-friction "bearings-adaptedfor'engagingsaid rib on either side thereof ,"a rack connected with said bar, and a gear train interconnectin said rack withsaid nut whereby movementofsaid carriage is effective axially'to shift said-leadscrew thereby to vary the eiTective pitchthereof, v

. KURT H. WILLS.

REFERENCES CITED The following'refernces'are of record in the file of this patent:

STAT ES PATENT s Number *Name Date 1,347,789 Muller "July 27, 1920 1,976,476 'Breitenstein Oct. 9, 1934 2184;377 "Bicke1' Dec."26, 1939 2,231,000 'Dris'sner' Feb. 11, 1941 

